1. Field of the Invention
The present invention relates to a disk array device.
2. Description of the Related Art
A disk array device for use as an external storage device in a computer system generally comprises hard disk drives, a controller, a power supply, a battery, an enclosure, and a fan. These components are placed within a single housing. In the event of a power failure, the battery supplies power so that cached data is written on a hard disk drive to automatically initiate and complete a planned shutdown for the purpose of avoiding the loss of cached customer data. When a disk array unit is added, the enclosure controls relaying and/or connection in relation to the added unit. In order to prevent the housing internal temperature from rising, the fan takes in air from the outside of the housing to forcibly replace internal air with external air.
It is highly requested that such a disk array device be downsized. However, the size of the disk array device generally increases with an increase in its storage capacity. This is because, since the use of a larger number of hard disk drives and a higher-performance controller is required to provide a large storage capacity, a large-size power supply and a cooling device have to be provided. To provide adequate cooling performance, it is also necessary to consider the device's internal ventilation. When a plurality of disk array devices of a greater size is added for use, the required installation area increases accordingly.
Under these circumstances, various techniques have been proposed with a view toward decreasing the size without sacrificing the cooling performance. For example, the technique disclosed by Japanese Patent Application Laid-open Publication No. JP-2001-338486-A separates a cooling air flow path into two. One path is used for the flow of cooling air provided by a fan that is attached to a power supply mule, which is mounted in the upper part of a disk array device. The other path is used for the flow of cooling air provided by a cooling fan module, which is mounted on a lateral surface of the lower part of the disk array device. Further, a heating element and a power supply module with a cooling fan are positioned after the air flow paths. This decreases the front-to-rear dimension of the disk array device without sacrificing the cooling performance.
However, the technique disclosed by Japanese Patent Application Laid-open Publication No. JP-2001-338486-A cannot reduce the height of the disk array device when the cooling air flow path is separated into the path for the cooling air provided by the power supply module in the upper part of the device and the path for the cooling air provided by the cooling fan module in the lower part of the device. Further, if the fan module in the lower part of the device becomes faulty, the device's lower part cooling efficiency decreases. Furthermore, a cooling fan is provided in both the upper and lower parts of the device. As a result, a large number of cooling fans are used for the whole disk array device.